Colin Kaepernick might have seven starts by now, but Jim Harbaugh’s midseason decision to bench Alex Smith and put the 49ers’ legitimate Super Bowl hopes in the hands of what amounted to a rookie quarterback finally faces a litmus test — the playoffs.

Should Kaepernick lead San Francisco to the NFC Championship Game with a divisional win over Aaron Rodgers and the Packers at Candlestick Park this weekend, Harbaugh’s gutsy roll of the dice will be instantly redeemed.

But should the Niners falter against Green Bay, especially if Kaepernick plays a key role in their demise, then Harbaugh can expect a long, loud and heavy dose of second-guessing.

Even Kaepernick appeared to realize that this week leading up to the most important game of his — and his head coach’s — NFL career.

“I’m trying to approach it as just another game, but there’s a lot more at stake,” Kaepernick said.

And not just for the option-running quarterback from Nevada who made such a splash on national TV against the Bears in place of the injured Smith and ended up winning five of his seven regular-season starts.

Harbaugh has even more at stake tomorrow night because there’s no going back to Smith, who is expected to depart after the embarrassment of losing his job due to injury despite leading the Niners to a 6-2-1 start this season and an NFC title-game appearance last year.

But if you think Harbaugh still harbors any second thoughts that he’s willing to admit publicly, well, you don’t know Harbaugh.

“[After Kaepernick’s first two starts], he was the healthier of the two quarterbacks and had played well,” Harbaugh said this week. “And then after that I saw enough really good things that I wanted to have the same faith and trust in Colin that we had shown in Alex.”

Harbaugh might have faith in Kaepernick, but he hasn’t been able to show any proof just yet that breaking one of the NFL’s unwritten codes — a player shouldn’t lose his job solely to injury — was worth it.

That’s because the Niners lost just as many games with Kaepernick under center — two — as they did with Smith this year. Not only that, but Smith also was playing some of the best football of his career at the time of his unceremonius benching (a 70 percent completion rate with 13 touchdown passes and just five interceptions).

And while Kaepernick’s dangerous ability as a runner (a trait Smith lacks) helped make him a sensation early on as San Francisco’s starter, defenses appeared to adjust as the season went on.

Kaepernick didn’t complete better than 57 percent of his passes in any of his final three starts while rushing for a total of just 64 yards, a sign that the second-year pro isn’t catching anyone off-guard the way he did the Bears on “Monday Night Football” two months ago.

Even more worrisome for the Niners, one of those three starts was a 42-13 destruction by the NFC West-rival Seahawks — a team San Francisco could very well face next week should Harbaugh’s team make it back to the conference championship.

But you’ll hear nothing but raves about Kaepernick from the 49ers camp this week, most of them centered on the calm and self-assured attitude he appears to be taking into tomorrow’s showdown.

“For Colin, it’s [just] another game, and I think the way he handles it day-to-day has been very mature,” San Francisco offensive coordinator Greg Roman said. “I don’t think we’re going to see any big eyes. He’s very businesslike day-to-day. Not concerned.”

Added Harbaugh: “His focus has been good. Very good.”

That’s in large part because Kaepernick doesn’t consider himself a second-year pro.

“This is my 17th year of football,” he said. “Football is football once you get on the field. You just have to raise your level of play [in the playoffs].”

For Harbaugh’s sake, Kaepernick needs to turn that talk into action tomorrow night.